Radio receiving apparatus



NOV. 28, 1933. w s STEWART 1,937,099

RADIO RECEIVING APPARATUS Filed NOV. 5, 1927 90 Volts 6 225mm 5Jvzz/emr.

Patented Nov. 28, 1933' iv i UNITED STATES PATENT O a 1,937,099RADIORECEIVING APPARATUS William Scott Stewart, Chicago, ApplicationNovember 5, 1927. Serial No. 2311189 v '5 Claims. (01.250 40) i Thepresent invention relates to a simplified densers of varying'range,sotha-t-one ormore form of tuning control for radio receiving appamay bebridged across the'circuit when lower ratus that allows of practicallyinstantaneous frequencies than may be attainable with only change fromone frequency to, another without one condenser are to be received. Alsoany of the necessity of carefully adjusting dials and. these condensersmay have aidefinite and-fixed 6Q; other control devices associated withsuch appacapacity. -j 7 j r a j v ratus; and which lends itself to readyoperation This arrangement alsogreatly increases the by even suchpersons as are unfamiliar with radio frequency range of the receiver to"which my instruments. present invention is. applied, as obviously the 1One of the objects of the present invention lowest frequency to whichthe receiver. may be is to provide a number of complete, but indetunedwill be that attained when all the conpendent, tuning units for theradio receiving set. densers are thrown across the, inductance .coil,These tuning units are capable of being thrown and the highest frequencywill be that when into and out of service by the mere throw of none ofthe condensers are thrown-across the a switch, and are independentlyadjustable so coil. For practical purposes, and to producea 70 thatanyone of the said tuning units may be receivingsethaving the powertoreceive electric I adjusted for a particular frequency. waves froma longdistance, and to produce suffi.--

It is the usual modern practice in radio recient power to allow the useof loud-speaking ceiving sets to control the frequency to which devices,it is usual to employa number of stages the set will respond, or motherwords the waveof amplification at high frequencies before, the 75,.-

length, by varying the inductance and capacity detector stage,such-amplification beingy com-w of the circuits associated with theamplifier and monly termed radio-frequency amplification-V detectortubes or other electric wave detecting Receivers incorporating suchradio-frequency devices. Thismay be accomplished by a numberamplification usually have two stages of this of different methods, asfor example by varying amplification, followed by a. detector stage, the

the inductance, as by use of a variometer or by signals obtained fromthe latterstage thenxbeing some device capable of changing the number ofpassed eitherthrough" a telephoneinstrument-or' coils of a solenoid orsimilar coil, by varying the further amplified at lower, or audiofrequencapacity bridged across such coil, as by the use cies to operatethe loud-speaking devicesalready 6.0 of a variable condenser; or byvarying both the referred to; In accordance with-,mypresent-in- 86inductance and the capacity. vention, no change is made in theaudio-fre- In the course of the development inthe art quency parts ofthe receiving. set. of constructing radio receiving apparatus, it has Afurther object of myinvention is to provide 7 become standard practiceto adjust the frequency, means whereby a radio receiver may be. tuned235 or, in more popular terms, to tune the reto a givenfrequency by oneof the condensers 90 ceiver by employing coils of fixed inductanceuandthat is bridged across the inductance coil by to tune the circuitassociated with said coils and closing a'switch, whereupon the said'switch may detecting and amplifying device by' means of be opened, andasecond-switch connecting a variable condensers bridged across suchcoils. second condenser may be' brought into service,

49 In accordance with my present invention 1 and this second condensermay then be tunedgto v provide an inductance coil for each amplifierafrequency different from that ofthefirstconelectron tube and for thedetector tube, but in- 'denser; and this may be repeated asmany timesstead of bridging such inductance with but one as thereare condensersprovided. This makesit variable condenser, I do so with a plurality ofpossible to tune the receiving settoa plurality.

i5 condensers, allhaving the same capacity and of sending'stations, anyof which may be incharacteristics, any of which condensers may bestantly tuned-in by throwing the corresponding thrown out of service bymeans of a suitable switch connecting the condenser that isadjustedswitch. It is contemplated to use but one of to tune in that particularfrequency. n these condensers at atime, and each one of In sets using'anumber of tuning units that -50 them is therefore chosen of suchcapacity range are cascaded, as for example insets using, two .105

that all of the desired frequencies, to-which the stages of tunedradio-frequency amplification receiving setincorporating mypresentinvention and one tuned detector stage, it.has becomecuswillrespond, may be attained by the use of but tomary to provide acondenserwforeaeh.ofithese one of these condensers. 7 However, it willbe stages. Formerly these condensers were; inde- 55 within the scope ofmy invention to have conpendently variable, but the most modernconlglOstruction is to vary the capacity of said condensers simultaneously.This is accomplished by either connecting the rotors of such variabledensers, each set, for example, consisting of three variable condensershaving their rotors mounted on a common shaft, and each of whichindividual condensers is electrically connected with a suitableinductance coil. Each of these sets of condensers may be thrown intoservicebya suitable switch. Provision is aiso made for locking theindividual sets of condensers in the position at which any desiredfrequency is tuned in at its maximum response, so that accidentaldisplacement of the condenser setby accidental movement of the dial ortuning-drum may be avoided. a In the drawing accompanying the presentapplication there is shown in Figures 1 and 2 a diagram of a standardradio receiver having audion tubes. The -audio-frequency amplificationassociated with the receiver is not shown, but merely indicated, as thisforms no part of my present invention. a

In this drawing, Fig. l is a diagram of the cirouits employed, showing aplurality of condenser setsbridged across suitableinductance coils, andshowing the switches employed'for throwing the various condenser setsinto the circuit.

Fig.2 is a top plan view showing one form of switchthat maybe employedfor connecting the condenser sets, when'the switch is closed; and 5 Fig.3 is a similar View showing the switch opemand. 7

Fig. 4 is a detail View of the condenser and dial arrangement; A

either directly to the ground 5, or through a variable condenser 6 shownin dotted outline.

One side of'the secondary coil 3-is connected with the grid of the firstradio-frequency amplifier electron tube 'l, and the other side of thecoil to one of the leads of the filament of thesaid electron tube, as iswell understood in this art.

The plate of the first electron tube '1 is connected to the primary 3 ofa second radio-frequency R'I'z, whose secondary 9 is connected to thegrid and filament of a second electron tube 10 in the same manner as theJ connections of electron tube 7. The plate of the second electron tube10 is connected with the primary ll of a third radio-frequencytransformer RTs, and

- thesecondary 12 of the said transformer 3T3 is connected tothe grid ofthe detector tube 13,

a small capacity grid condenser and grid leak 14 being employed inaccordance with the'wellknown principles of the radio receiverconstruction art." The plate of the detector tube 14 is connected withthe primary of an iron-core audiotransformer AT1 inthe usual fashion,which requires no description, as this is'now standard practice,- andforms'no part of the present invention. I

The secondaries 3, 9 and Bare bridged by a plurality of condensers C1,C2, C3, C4 and Cs; ca 02a etc; and Clb, Czb etc. as shown on the drawing(Fig. 1), and switches S1, S2 and S3 are provided to connect suchcondensers across the said secondaries. It is to be understood that thecondensers C1, Ca and Clb are on a single shaft and are thereforevariable simultaneously. The same is true or" condensers C2, C22. andC2b, and of the othercondensers bearing the same series of numbersas C3,(33a and Cat etc.

. One side of the said condensers, and preferably the stator side, ifrotary condensers are employed,

' is permanently connected to thefilament return side of the saidsecondaries, and the other, preferably'the rotor side, connected to oneterminus of the switches' in order to throw any one set of threecondensers into the circuit, a switch having the general form shown inFigs. 2 and 3 may be used, although it is within the scope of myinvention to use any other form of convenient switching arrangement. I

In Figs. 2 and 3' it will be seen thatI provide a non-conducting shaft15 having three conduct-'- ing knife-blades l6 capable of engagingsuitable prongs The be con'tr ed by a dial oi'handle l8, and the saidshaft may pass through the panel 19. Wires 20 and 21 serve to connectthe switch terminals with the second. coils 3, 9 and 12, as alreadyexplained. A set of set of condense: five in the present case.

The operation of a radio receiver constructed in accordance with mypresent invention is as follows: 1

15 is rotatable and may switches provided'for each Supposing for examplethat the switch controlprinciples, and as shown diagrammatically inFig.1, the receiver may then be tuned to a given frequencycorrespondingto that of the sending stationthat is to be tuned in, for example onesending on a frequency of 979 kilocycles, and

which will for convenience be designated as Station A. This willcorrespond to a certain dial setting on the dial ordrum-associatedwiththe shaft of the rotor of the condenser set then inuse, namely condensers C1, C15 and Clb. When the maximum clarity andvolume of signal is tuned in for station A, then a suitable set screw istightened down against the dial or drum of the said condenser so as'toprevent the accidental detuning of the said set of condensers, Onemethod of accomplishing this is shown in Fig. 4, in which the rotors ofthe condensers C1, C15. andCib are shown mounted on a common shaft 22,rigidly connected with a'dial 23 passing through a panel 23-1. Asuitable bracket 2 L mounted on the said panel and bent so as toslightly cover the said dial 23 bears a screw 25 having a milled head26:, and

by turning the said screw the dial 23 maybe locked into position.

If thereupon the switch associated with condenser set 01, Cm and Clb isopened, and the switch say StationBfsending on a frequency, forexample-of 6 H) kilocycles. Thereupon, in win,

this condenser may be thrown out of the circuit ,by opening its switch,"and one of the other condenser sets may be thrown into service andtuned for their particular station. I

It will be seen that the setting for Station A,

on condenser set C1, etc., will remain unchanged, and the user of thereceiver may return to the setting for Station A merely by throwing inthe required switch associated with the said condenser. This makes theoperation of a receiver incorporating my present invention very easy,for after the set has been tuned for the stations that are to bereceived, any one may tune'in any of the given stations by the merethrow of a switch. This is particularly valuable when the receiver is tobe operated by inexperienced persons, when the tuning may be done by anexperienced operator, and the condenser setting thereupon locked. Allthat the inexperienced user then needs to know is the number of theswitch corresponding to the station that is to be tuned in.

Any number of independent condenser circuits may be introduced into thecircuit, although only five are shown, as this is purely a matter ofconvenience. The regular operation of the set is in no way disturbed, asfour of the condensers may be permanently set for four differentstations,

and the fifth one may be used for tuning any de- I sired station, evenincluding those that are permanently tuned in, so that it becomespossible, for example, to employ the time between the numbers of aprogram that is being received to listen to other stations, and theninstantly to return to the regular program without changing the settingof the adjusted condensers. Obviously, the condensers to be setpermanently may be of the fixed type, and I am not to be limited to theuse of variable condensers throughout, nor to the particular types ofvariable condensers, as types other than those having rotors and statorsmay be employed.

Obvious modifications of the arrangement shown are to be understood asbeing within th scope of my invention.

What I claim is:

1. In a radio receiver a plurality of, sets of,

ganged condensers, simultaneously variable by a single control, each setbeing independently variable, inductances common to all of said sets ofcondensers, and means for selectively electrically connecting said setsof condensers with said inductances.

2. In a radio receiver a plurality of sets of ganged 1 condenserssimultaneously variable by a single control, each set beingindependently variable, inductances common to all of said sets ofcondensers, means for selectively electrically connecting said sets ofcondensers-with said inductances, and means for preventing theaccidental variation of the setting of the said sets of condensers. p

3'. In a radio receiving set means for perma- 'nently tuning said set toa given number of sende ing stations without impairing the ability ofsaid set to be tuned to stations other than those to which it ispermanently set, which comprises in- I ductance coils, sets of gangedvariable condensers each set varied by a single control and being, 7bridge across said coils for tuning said coils to anyfrequency withinthe. range of thecombination of said coils and said sets of condensers,

means for connecting and disconnecting the incuit changing devices'forintroducing any one of the sets of condensers into said circuits.

' 5. In a radio receiving set having a plurality of inductance coils andassociated circuits, means for selectively tuning said coils to aseriesof fixed frequencies, comprising the combinationv of a plurality of setsof ganged condensers simultaneously variable by a single control, andmeans for connecting anyone of the said sets of condensers into thesystem as a unit by suitable switchin means.

, WILLIAM SCOTT STEWART.

